Controlling VAV systems may not be as simple and direct as many may have thought. There are many, many nonworking or partially working systems, as a result of incomplete or nonfunctioning controls. When specifying the total system, the designer must consider the interaction of the individual control loops and be certain to specify the desired results. One should not attempt to specify each individual control component.

Since different manufacturers may provide the same results in a different manner and with different components, the results are more important to the designer than the method or equipment used. Once the required results are specified, the designer should be prepared to confirm compliance by detailed submittal review and, even more importantly, by field test prior to system acceptance. It is crucial that all system components, fans, terminal boxes, and controls are compatible to ensure achievement of the required total system operating characteristics.

In this paper, the author will present some ideas about t/qe interactions of the various control loops and suggest solutions to some specific areas of concern.

Units: I-P